OBJECTIVES: To determine optimal particle size for a colloidal suspension to be used for increasing absorption coefficients of the liver and facilitate the detection of small hepatic metastases. METHODS USED: There have been considerable unexpected difficulties and delays with the extraction and exact quantitation of the latex particles following intravenous injection. Last year we were finally able to extract these particles with Tolune from the animal tissues and quantitate them by fluorometry. The exact details of the quantitation technique are still under experiment. Once we have finalized the technique, the optimal particle size for hepatic deposition will be determined. SIGNIFICANCE OF RESEARCH: We are trying to demonstrate that certain organs preferentially take up intravenously injected particles of specific diameters. This would prove to be a significant help in the development of an ideal intravenous contrast material for the opacification of the liver and spleen and may facilitate earlier detection of small liver metastases on computerized tomographic examinations of the liver and spleen.